Processes employed to date for the production of lithium hydroxide monohydrate from lithium chloride have typically utilised either electrolysis of lithium chloride, such as that described in U.S. Pat. No. 3,597,340, or the conversion of lithium chloride into lithium carbonate by soda ash, such as that described in U.S. Pat. Nos. 8,691,169 and 8,669,260, followed by the causticisation of lithium carbonate so formed with hydrated lime, such as that described in U.S. Pat. No. 4,207,297.
The above described processes of the prior art are known to be relatively expensive and inefficient. For example, the production of lithium hydroxide monohydrate from the electrolysis of lithium chloride utilises very high quantities of electricity, in the order of >5,000 KWh/MT of LiOH.H2O, and the current efficiency is lower than 65%, see US Patent Publication 2012/0107210. The production of LiOH.H2O from lithium carbonate using hydrated lime causticisation is expensive as it first requires the production of lithium carbonate from lithium chloride, followed by causticisation using expensive purified hydrated lime as a raw material. In turn this produces a relatively impure lithium hydroxide monohydrate product. The hydrated lime introduces calcium impurities into the lattice of LiOH.H2O which has to be purified by expensive known methods, thereby increasing the cost of production. This is particularly problematic when attempting to produce high purity battery grade lithium hydroxide monohydrate, such as that having greater than 99.9% purity by weight.
The process of the present invention has as one object thereof to overcome substantially one or more of the above mentioned problems associated with prior art processes, or to at least provide a useful alternative thereto.
The preceding discussion of the background art is intended to facilitate an understanding of the present invention only. This discussion is not an acknowledgement or admission that any of the material referred to is or was part of the common general knowledge as at the priority date of the application.
Throughout the specification and claims, unless the context requires otherwise, the word “comprise” or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.